1. Field of the Invention
This invention relates to a novel process for preparing high molecular weight polysulfide polymers from polythiodiglycol. The polythiodiglycol is polymerized with means for removing the water of reaction to a low molecular weight prepolymer provided with halogen terminals; these halogen-terminated polymers are then reactable with alkaline or alkaline earth polysulfides to form a latex dispersion of very high molecular weight. This dispersion can then be converted to --SH terminated polymers by the usual methods.
2. Description of the Prior Art
As is well known, polysulfide polymers are conventionally made by the reaction of alkaline or alkaline earth polysulfides with polyhalogenated organic compounds. Particularly used in this reaction are sodium polysulfide, Na.sub.2 S.sub.x, and dichloro compounds, Cl--R--Cl, wherein x, the average value or rank of the polysulfide, is 2.25, and the dichloro compound is bis(2-chloro-ethyl)formal. The general reaction is: EQU nNa.sub.2 S.sub.x + nCl--CH.sub.2 CH.sub.2 OCH.sub.2 OCH.sub.2 CH.sub.2 --Cl .fwdarw. --CH.sub.2 CH.sub.2 OCH.sub.2 OCH.sub.2 CH.sub.2 S.sub.x --.sub.n + 2nNaCl
As can be seen, the consumption of chlorine and the amount of waste sodium salts is excessive especially considering the fact that for a polymer in which n is usually in the range of 2,000 to 4,000, 4,000 to 8,000 moles of sodium salts must be discarded. Also considerable quantities of a sodium polysulfide byproduct, Na.sub.2 S.sub.2 O.sub.3, must be discarded as waste.
U.S. Pat. No. 2,728,748 to F. O. Davis discloses a reaction in the presence of solvents of dithiodiglycol with formaldehyde and bis -- 2-chloroethyl) formal to produce polysulfide polymers. The invention of this application distinctly differs from the Davis patent wherein it is stated that to get chlorine terminals on the resultant polymer, when bis -- 2-chloroethyl) formula is used, one must have the ratio of dithiodiglycol to formaldehyde less than 1.00. As will be seen by some of the examples herein, firstly, this new process may be performed in the absence of any solvents, and secondly, even if the ratio of dithiodiglycol to formaldehyde is almost 3 the novel process of this invention produces chlorine terminals on the low molecular weight polysulfide polymer although the resultant polymer will contain a slightly different backbone between the sulfur linkages. Therefore, even though there appears to be similarities in the reactions, the complete refutation of the solvent requirement and the required of Davis dictates that there must be differences such that the processes must be dissimilar. Additionally, Davis uses a dichlorinated organic material, whereas this invention uses either inorganic halogenating agents or monohalogenated organic compounds to produce the halogen terminals which will react with the alkaline or alkaline earth polysulfides.